Update entry.S

[Abhinavpatel00]

corrected the typo here

# Read the hardware thread ID ('mhartid') into register 'a1'.
csrr a1, mhartid

# Increment the hardware thread ID by 1 to avoid a stack overlap issue.
addi a1, a1, 1

# Calculate the new stack pointer value:
# sp = stack0 + ((hartid + 1) * 4096)
mul a0, a0, a1
add sp, sp, a0

[echtwerner]

This change is similar to the request made in PR #252.

@maintainer, if you do not wish to acknowledge this PR because it goes against one of the objectives of the learning experience, it would be appreciated if you could close this PR to keep the repository clear and focused.